This invention relates in general to respirators and in particular to a new and useful respirator having a closed respiratory gas circulation line.
Respirators, and this is particularly true for apparatus with an open circulation and for respirators with closed circulation described here, should have a slight overpressure, compared to the ambient atmosphere in circulation in each phase of the breathing process. In this case, no ambient air can penetrate e.g. in a leakage of the mask sealing edge, even in the inhalation phase.
The excess pressure in the closed circuit requires, however, in this case an outflow of the relatively small oxygen supply to the outside; high concentrations of O.sub.2 could then also become hazardous in fighting fire.
In immersion technology it is necessary to fill up the breathing gas volume by controlling the O.sub.2 content, due to the rising ambient pressure.
A known respirator with circulation of the breathing air forms the circulation over a breathing bag, a CO.sub.2 binding cartridge, as well as an inhalation and exhalation hose to the face mask and the diver helmet respectively. In this closed circuit, an equalizing gas bottle introduces inert gas over a valve controlled automatically by the pressure when the pressure difference between the breathing bag and the environment rises when the ambient pressure is increased, e.g. in diving, and the breathing gas volume in the breathing bag diminishes by the rising ambient pressure and no longer suffices to fill the lungs. An oxygen bottle supplies oxygen into the breathing bag over a pressure reducer and regulating valve through a line. The control of the oxygen line is effected over an oxygen sensor, arranged in the breathing bag or in the inhalation tracts. The oxygen supply is thus always effected in dependence on the oxygen consumption.
There is no control here of the equalizing gas over an automatic lung for each breath, and no control of a constantly lower overpressure, compared to the ambient pressure. Besides, the equalizing gas, here inert gas, will further reduce the oxygen concentration for breathing, depending on the immersion depth. A complicated control would be required for the equalization (German Pat. No. 1,104,828).
Another known respirator concerns a device for maintaining a predetermined gas mixture or an atmosphere, particularly a device for maintaining and regulating the desired amount of oxygen in a gas mixture to be inhaled.
The breathing gas is conducted in a cycle in which the carbon dioxide is absorbed in a device. The spent oxygen is supplied from a storage tank, in addition an equalizing tank is provided for a neutral gas.
The oxygen is determined over a detector and controlled correspondingly from the storage tank. The valve arrangement comprises a correspondingly controlled valve, as well as a constantly open valve, which permits a continuously predetermined minimum flow. A nuetral gas is supplied from the equalizing tank into the cycle over a valve in the breathing bag working in dependence on the immersion depth.
What has been said above, applies here too. There is no control of the equalizing gas, here of the neutral gas, e.g. oxygen or helium, with the breathing pauses over an automatic lung, but by a utility valve, which introduces so much neutral gas into the breathing bag in dependence on the water pressure that this bag is kept inflated (DE-OS No. 14 34 935).